JP3216665B2 - Eddy current type reduction gear - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an eddy current type speed reducer for assisting a friction brake of a large vehicle, and more particularly to an outer peripheral wall of a guide cylinder having a box-shaped cross section made of a non-magnetic material disposed inside a brake drum. The present invention relates to an eddy current type speed reducer in which a number of ferromagnetic plates are connected at equal intervals in a circumferential direction, and switching between braking and non-braking is performed by forward / reverse rotation of a magnet support cylinder disposed inside a guide cylinder. .

[0002]

2. Description of the Related Art In an eddy current type speed reducer disclosed in Japanese Patent Application Laid-Open No. 1-298948, a guide cylinder having a box-shaped cross section made of a non-magnetic material is disposed inside a brake drum, and the guide cylinder has an outer peripheral wall. A large number of ferromagnetic plates are connected at equal intervals in the circumferential direction, and a magnet (herein referred to as a permanent magnet) facing each ferromagnetic plate is connected to a magnet support tube rotatably supported in the inner space of the guide tube. By changing the phase of the magnet support cylinder by half the pitch of the ferromagnetic plate, switching between braking and non-braking is performed.

As shown in FIG. 5, in the above-described eddy current type speed reducer, the magnet 24F of the magnet support tube 14 is
Are arranged side by side so that the polarity with respect to the ferromagnetic plate 15 is alternately different in the circumferential direction. When not braking,
When the magnet 24F is shifted by half a pitch with respect to the ferromagnetic plate 15, the ferromagnetic plate 15
A short-circuit magnetic circuit 27 is formed over the F and indicated by a chain line. However, the magnet 24F exerts a magnetic field on the braking drum 7 via the gap t between the adjacent ferromagnetic plates 15, and may form a magnetic circuit 27a indicated by a broken line. The rotating brake drum 7 receives a drag torque as it crosses the leakage magnetic field.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a magnetic field that leaks from a magnet to a braking drum through a gap between ferromagnetic plates during non-braking without impairing braking performance during braking. The present invention is to provide an eddy current type speed reducer that effectively suppresses drag and suppresses drag torque.

[0005]

In order to achieve the above object, according to the present invention, a guide cylinder having a box-shaped cross section made of a non-magnetic material is provided inside a brake drum connected to a rotating shaft. A large number of ferromagnetic plates are connected to the outer peripheral wall of the magnet at equal intervals in the circumferential direction. The magnets are coupled such that the polarities of the magnets are alternately different in the circumferential direction, and the outer peripheral walls of the magnets are provided with magnetic poles opposite to the opposite ends at the center in the circumferential direction.

[0006]

When braking, each ferromagnetic plate entirely overlaps each magnet of the magnet support cylinder. The magnetic field of each magnet penetrates the ferromagnetic plate and acts vertically on the inner peripheral surface of the braking drum. When the rotating brake drum crosses the magnetic field of the opposite direction in the circumferential direction, an eddy current flows through the brake drum, and the brake drum receives a braking torque.

When the magnet support cylinder is rotated by half the pitch of the ferromagnetic plate during braking, the ferromagnetic plate straddles two adjacent magnets having different polarities, and the ferromagnetic plate and the magnet support cylinder are connected to each other. A short-circuit magnetic circuit is formed therebetween. The center of each magnet faces the portion between the ferromagnetic plates on the outer peripheral wall of the guide cylinder, but the center of the outer circumferential surface of each magnet in the circumferential direction is a magnetic pole opposite to both ends, so the center of each magnet Forms a short-circuited magnetic circuit with both ends. Accordingly, the leakage magnetic field exerted on the braking drum by the central portion in the circumferential direction of each magnet via the outer peripheral wall of the guide cylinder becomes very weak, and the braking drum does not receive drag torque.

[0008]

1 is a side sectional view of an eddy current type speed reducer according to the present invention, and FIG. 2 is a front sectional view thereof. An eddy current type speed reducer according to the present invention includes a braking drum 7 made of a conductor coupled to an output rotation shaft 1 of a vehicle transmission, for example, and a braking drum 7.
Guide tube 10 made of a non-magnetic material disposed inside
And a magnet support tube 14 rotatably supported in the inner space of the guide tube 10. The brake drum 7 overlaps the flange portion 5a of the boss 5 with the end wall of the brake drum 3 of the parking brake on the mounting flange 2 which is spline-fitted and fixed to the rotating shaft 1, and has a plurality of bolts 4 and nuts. Is concluded. Numerous spokes 6 extending radially from boss 5
Is connected to one end of a braking drum 7 having a cooling fin 8.

The guide cylinder 10 having a box-shaped cross section is constituted by connecting an annular lid plate 11 to a cylinder having a C-shaped cross section, for example. The guide tube 10 is fixed by a suitable means to, for example, a gearbox of a transmission. The guide cylinder 10 has a number of ferromagnetic plates (pole pieces) 15 coupled to a number of openings 25 provided on the outer peripheral wall 10a at equal intervals in a circumferential direction (see an arrangement pitch p shown in FIG. 5). Preferably, the ferromagnetic plate 15 is cast when the guide tube 10 is formed. The magnet support tube 14 is an inner space of the guide tube 10,
Specifically, it is rotatably supported by the bearing 12 on the inner peripheral wall 10b.

Preferably, three actuators 20 are connected to the left end wall of the guide cylinder 10 at equal intervals in the circumferential direction. The actuator 20 has a piston 17 fitted on a cylinder 18, and a rod projecting outward from the piston 17 is connected to an arm 16 projecting from the magnet support cylinder 14 through an arc-shaped slit 18a on the left end wall of the guide cylinder 10. Is done.

As shown in FIG. 2, a magnet support tube 14 made of a magnetic material has magnets 24 facing each ferromagnetic plate 15 one by one.
Are arranged so that the polarities facing the ferromagnetic plate 15 are alternately different in the circumferential direction.

According to the present invention, each magnet 24 is provided with a magnetic pole opposite to both ends at the center of the outer peripheral wall in the circumferential direction. That is, the magnet 24 facing each ferromagnetic plate 15 is divided into three in the circumferential direction, and the polarity of the magnet 24A at the center is changed to the magnet 24 at both ends.
B is connected in the opposite direction to the polarity of B. However, in practice, the magnet 24 is formed by molding a magnet material into a predetermined shape, and then magnetizing both ends to the magnet 24B and the center to the magnet 24A.

The magnet 24 is a substantially rectangular plate having a uniform thickness, and is curved in an arc shape so as to be in close contact with the outer peripheral surface of the magnet support tube 14. To obtain a strong magnetic field, the magnet 24
Is formed by molding a mixed powder of Nd-Fe-B, rare earth or the like, sintered, and bonded to the magnet support cylinder 14 with an adhesive, a bolt or the like.

Next, the operation of the eddy current type speed reducer according to the present invention will be described. As shown in FIG. 3, during braking, each magnet 24 entirely opposes each ferromagnetic plate 15 and
A magnetic field is applied to the braking drum 7 through the step 5. When the rotating brake drum 7 crosses the magnetic field, an eddy current flows through the brake drum 7, and the brake drum 7 receives a braking torque. At this time, the magnetic circuit 2 is transferred from the magnet 24 to the ferromagnetic plate 15, the braking drum 7, the adjacent ferromagnetic plate 15, the adjacent magnet 24, and the magnet support cylinder 14.
9 results. The magnet 24A at the center is the magnet 24B at both ends.
, A short-circuit magnetic circuit 28 is always formed,
Since the magnet 24A at the center has a smaller capacity (magnetic field strength) than the magnets 24B at both ends, the magnet 24A has almost no effect on the braking ability during braking.

As shown in FIG. 2, when the magnet support cylinder 14 is rotated by the actuator 20 by half the pitch of the ferromagnetic plate 15 by the actuator 20, the two adjacent magnets 24 are brought into contact with the common ferromagnetic plate 15 during non-braking. opposite. A short-circuit magnetic circuit 27 is generated between each ferromagnetic plate 15 and the magnet support cylinder 14, and the magnet 24
Does not apply a magnetic field to the braking drum 7.

At the time of non-braking, the magnet 24A at the center is the guide cylinder 1
0, facing a portion between the ferromagnetic plates 15 and 15,
Since the short-circuit magnetic circuit 28 is formed between the magnets 24B at both ends, the magnetic field leaking to the brake drum 7 via the outer peripheral wall 10a of the guide cylinder 10 is extremely weak, and the brake drum 7 receives almost no drag torque. .

In the embodiment shown in FIG. 4, each magnet 24 is formed integrally from a magnet material, and then the inner peripheral wall is formed on the S pole (or N pole).
And at the same time, both ends of the outer peripheral wall are N pole (or S pole).
Poles), the center of the outer peripheral wall in the circumferential direction is a magnetic pole 24 opposite to both ends.
C is magnetized respectively. This simplifies the configuration of each magnet 24 and facilitates assembly to the magnet support tube 14.

[0018]

As described above, according to the present invention, a guide cylinder having a box-shaped cross section made of a non-magnetic material is disposed inside a brake drum connected to a rotating shaft, and the guide cylinder is provided on an outer peripheral wall of the guide cylinder at equal intervals in a circumferential direction. A large number of ferromagnetic plates are coupled, and the magnet support cylinder rotatably supported in the inner space of the guide cylinder has a polarity different from that of the ferromagnetic plate in the circumferential direction alternately corresponding to each ferromagnetic plate. The magnets are connected as described above, and the outer peripheral wall of each magnet is provided with magnetic poles opposite to those at both ends in the circumferential center, so that when braking is not performed, a pair of adjacent magnets have a common strength at both ends. Facing the magnetic plate, each magnet forms a short-circuit magnetic circuit between the magnet support cylinder and the ferromagnetic plate, and does not apply a magnetic field to the braking drum.

In particular, the center in the circumferential direction of each magnet faces a portion between two adjacent ferromagnetic plates on the outer peripheral wall of the guide cylinder, but the center in the circumferential direction of each magnet has magnetic poles opposite to both ends. Therefore, a short-circuited magnetic circuit is generated between the central portion and both ends, and the strength of the magnetic field leaking from the circumferential central portion of each magnet to the braking drum through the space between the adjacent ferromagnetic plates is extremely weak, and exerts an influence on the braking drum. The drag torque becomes negligible, and power loss can be suppressed.

Since each magnet has a substantially uniform thickness, molding is easy, and the strength of the magnet itself and the strength of coupling with the magnet support cylinder are not impaired.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an eddy current type speed reducer according to a first embodiment of the present invention.

FIG. 2 is a partial front cross-sectional view showing a relationship between a ferromagnetic plate and a magnet support cylinder when braking is not performed in the speed reducer.

FIG. 3 is a partial front sectional view showing a relationship between a ferromagnetic plate and a magnet support cylinder during braking in the speed reducer.

FIG. 4 is a front sectional view of a magnet of an eddy current type reduction gear according to a second embodiment of the present invention.

FIG. 5 is a side sectional view of a conventional eddy current type speed reducer.

[Explanation of symbols]

1: rotating shaft 7: braking drum 10: guide cylinder 14: magnet support cylinder 15: ferromagnetic plate 24, 24B: magnet 24
C: Magnetic pole

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-298948 (JP, A) JP-A-3-86063 (JP, A) JP-A-4-12660 (JP, A) 43786 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02K 49/02 H02K 49/10

Claims (1)

(57) [Claims] 1. A guide cylinder having a box-shaped cross section made of a non-magnetic material is disposed inside a brake drum connected to a rotation shaft, and a number of ferromagnetic plates are connected to an outer peripheral wall of the guide cylinder at equal circumferential intervals. A magnet is coupled to the magnet support cylinder rotatably supported in the inner space of the guide cylinder such that the polarity with respect to the ferromagnetic plate is alternately different in the circumferential direction, one for each ferromagnetic plate. An eddy current type reduction gear, comprising magnetic poles opposite to both ends at the circumferential center of the outer peripheral wall of the magnet.